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Discussion on ideal diesel fuel temps...

G

great white

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Looking for input gents.

I've read a few things that seem to indicate that 145-155 F is right around the best temp compromise between power production and atomization of diesel fuel. For example:
http://www.google.ca/url?sa=t&sourc...sg=AFQjCNFCklpxVOEKtGjeBIRQqdyZfomgKQ&cad=rja

(yes, I know they're selling something so it's suspect, but I've seen the number elsewhere also)

Although, 145-155 seems kind of high to me. But I'm not a petro-chemical engineer either.......

I ask because I'm getting ready to design the fuel supply and return system for my 98 6.5

The raptor 100 is waiting, as is the Racor prefilter with integrated fuel heater and water sensor.

To be decided is to install the cooler or not and where it shall be located.

Anyone have fuel temperature measurements from running a 6.5?

If you do have fuel temp measurements, do you run your truck in a predominately hot/cold/variable climate?

Let's have a good technical discussion with references here gents. Please, no "the colder fuel the better IMO" without substantiation or consideration of fuel waxing.

Please discuss....
 
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well, the colder the fuel is not better, I will start with that. Diesel fuel atomizes better and combusts better at higher temp, so running with the fuel heater makes sense. When I get home I will look at some snapshots of normal driving and high speed runs and what not to see if fuel temp varied at all. I'm pretty sure its usually around 120F.

And I suppose the 145F temp came up because that is where diesel will combust, but not its autoignition temp. So for all of the fuel to combust it has to reach 145F in the cylinder. If its too cold it might get pushed out and make smoke or haze in the exhaust.
 
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Hmm, chart available here http://www.tdiclub.com/articles/Diesel_Fuel_Guidlines/ seems to indicate 100-125 F would be an "ideal" for a flashpoint. That's a recommended "standard" as I understand it, poorer fuels would most likely have a higher flash point leading to a higher recommended temp I would think.

Have also been reading a few tech papers and it seems higher fuel temps can lead to retarded timing in diesels. Unless I'm turned around backwards here, that makes sence as the conmbustion would occur at a higher rate due to being above flashpoint and closer to autoignition points. Wait, msybe I am mixed up here: faster ignition would lead to advanced timing would it not? Need to sit and think about that one a bit....

But for temps, I need to find a happy medium here.

Truthfully, I'm beginning to think the actual temp (as long as it's not stupid high or gelling cold) is less important to my purposes for tuning than it is for it to be a consistent temp...
 
As you have posted it will have an effect on timing, and efficiency. If you pump up the fuel volume as much as I have you will need good atomization. Another reason I recommend higher pop injectors too.

If the fuel is hotter it will cause the fuel to burn faster so you can retard the timing of injection because combustion will happen faster after ignition. Diesel and Gas work differently, gas flash point is so low that it will burn/explode at any temp, so the colder you get it the more energy it will have in it. But for diesels we will get the most just by burning efficiently what we put in.

120F is probably a good place to be, or at least a good place to start. You can get that data from the scanner and maybe test out colder temps to see how it affects power and efficiency. For power you might want cooler, but efficiency warmer. Same with engine temps, for power you might like being at 185F, but for efficinecy would want to run in the are of 200F.

Whats real messed up is if you buy fuel from a place that kept their fuel warm so it expanded and has less energy in it.
 
I went back and looked at my screenshots looks like my fuel temp averages about 100F, but I have snapshots from 90F to 120F. I have snapshots from half dozen others and one of them is like mine, 3 of them average 120F, up to 140F (which I think is close to the scanners limit and excessive), and one of them averaged like 70F which is too low and might be why he is having economy problems (heater failure maybe).
 
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Hmmm, the TCV on my heater opens at 60 and closes at 90, good to stave off any waxing in winter but too low to reach the target temps it looks like we want.

Maybe I don't need to plumb in a cooler after all if most run around 140 F, given Buddy's info would be California like temps and I'm in Canada.

Maybe a temp bypass opening at 140-150 F for a cooler would be a good idea.

As I mentioned earlier, I think i'm going to gain more by a consistent fuel temp rather than a hot or cold one.

The fewer variables when tuning the better...
 
Mostly what I have learned with the long gone Duramax of mine can apply to your question.

A loaded 2008 6.6 Duramax will start to 'ping' after a sustained hill. This is in AZ with high outside or 'summer' temps for most of you including Canada. Yes, ping, just like a gasser sound.

This is due to everything under the hood getting hot including stupid high boost. No mechanism to cut back boost or retard timing exists in the computer for 2008. So the engine is over advanced just by getting hotter and specifically to a heat soaked intercooler and the resulting high intake air temps. A forced downshift for more engine cooling fan RPM helps. EDIT: High intake air temps evaporate and ignite the injected fuel quicker thus the advance on the timing as I reference it above.

The exposed fuel injector lines on any diesel will heat the fuel some with the engine cooling fan on.

From killerbee's website in regards to 'water' fogging before the turbo compressor:
"
The energy absorbed to evaporate a pound of 80 degree water is 700% more than required to heat (or cool) that same water by 100 degrees. Cooling the water first is too much trouble for too little benefit.
"

The above said I suggest you get more bang for your buck working on intake temps and advancing the timing with that. Simply because you get more difference in timing from intake temps than fuel temps looking at the factor from water above. Or at least it will put fuel temps in perspective as your project may be looking for every little bit of performance and or economy like hotrodders do...
 
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Acesneights1 said:
Just wanted to say, an excellent choice. I have one. Did you buy just the LP or the whole LP kit for 6.5TD with wiring ? If you want to spin that into a separate thread...Alot of us would like to know I'm sure.
Click to expand...

Bought the whole kit so I could get teh full warranty. May or may not use all of it or a part of it, haven't decided yet.

A seperate thread will be forthcomming for the entire fuel system install, but I don't want to get into it just yet.

Here's a bit of an overview though:

Raptor 100, racor MD57 prefilter, FTB ver2.0, fuel cooler, etc.....
 
great white said:
Hmm, some anecdotal evidence seems to indicate the new ULSD fuels can have lubricity problems above 100F...
Click to expand...
Well, the problem is that the ULSD wholsale is available with or without additive in it. Since most gas stations are cheap....'s They save the .006 of a cent and buy the plain stuff. I run the good stuff as I buy it wholesale and have not had any issues.
This is what I use as I am a Global reseller. Perhaps the product info sheet will give you some info.
http://www.globalp.com/products/product.cfm?productID=45
 
Matt Bachand said:
Keep in mind the fuel also cools the IP (and PMD) as well as lubricates it.
Click to expand...

PMD isn't a problem:

DSC03739.jpg


Most guys are probably running around the 100-140 rane and don't know it.

I'm looking to stabilize it in a range for tuning consistency and cold weather concerns.
 
For cooling you could check a junkyard with a smashed up Duramax...

Due to the high pressure injection system on the 2008 Duramax and the heat generated in the regulator valve the truck has a fuel cooler factory equipped in front of the fuel tank. It looks like a trans cooler with steel plates that have little holes drilled in it for rock protection. Temperature control and if it is on the return line etc you would have to look into.

Because it is GM it is only on there to control an extreme temperature problem that saves GM money in warranty repairs or stuff burning to the ground. Otherwise it would not be allowed to be added by the bean counter division... :nonod:

I don't know how the system deals with Gelling issues.
 
Probably because it has to be ULSD compliant, and it aint enough lubricity at high temps. Or the electric injectors which already fail a lot couldnt take the heat. But the DMax runs so much more boost and can atomize the fuel better with the direct injection that they may be able to run cooler fuel to get more power in the cylinder.
 
I read some stuff a good while back and as you would imagine the rules of thumbs differ according to history and differ with newer IP config's. Newer trucks have hotter ecm's electronics cooled by the fuel coming from tank and the cooler is on the return maybe to keep tank from warming too much and expanding fuel and causing air to vent. The cooler removes excessive heat (from electronics and higher rail pressure compression). Then the tank can normalize it and it again will cool electronics on path going to IP (or common rail pump). Common rail is designed and compensates for higher fuel temp of higher pressure.

Fuel should be blended not to gell in tank but the filter is the more real danger hence the filter manager heater of the 6.5 era.

In the days back they did not like fuel above 70F but newer IP's especially the GM DB/DS pumps were supposedly designed to run warmer being in the valley of the engine. And with lower lubricity fuel of there time in comparison to 1970's / early 80's ???

Read marine engines (warm environment) engines use to suggest a fuel cooler.

As the temp rises viscosity decreases and lubricity too. Not so much lubricity for bio fuels but viscosity still does. I notice a difference adding Sae 30 ND oil to fuel because I think it increases viscosity and lessens pumping slippage. This is more function of viscosity film strenght etc because it seems to work better in my old IP than 2 cycle oil or Optilube XP or other lubricitiy additive (and I can tell a difference in different stations that probably run different bulk additives and blend ratios of bio and freshness of fuel etc).


At first I thought just maybe one of the benefits to feeding the beast was better circulation of fuel and maybe better optimized fuel temp. And iirc TD posted back he did not really measure much difference at scanner reading (optic temp sensor) before / after FTB. And either he posted or I think I remember reading somewhere ??? I want to say 70 or 78 F measured at the fuel manager was preferred No. 2 fuel temp (again for the supply temp). But have never seen that correlated to optic sensor temp which I think would be a bit higher due to compression of fuel and warmth of valley of engine and hence IP.


Warmer fuel will burn quicker seen that lighting burn piles.
 
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